Visual detection of anti-icing fluids freezing by a low-temperature viscosity-sensitive aggregation-induced emission probe

Icing detection is critically important for preventing safety accidents and economic losses, especially concerning ice formation from invalidated anti-icing fluids (water and ethylene glycol) under extreme conditions. Traditional technologies like ultrasonics and capacitor-antenna face challenges with limited detection areas, lower accuracy, and susceptibility to electromagnetic interference. Here, we introduce a novel viscosity-ultrasensitive fluorescent probe 4′,4‴-(2,2-diphenylethene-1,1-diyl) bis-(3,5-dicarboxylate) (TPE-2B4C) based on AIEgens for monitoring ice formation of anti-icing fluids in low-temperature environments. TPE-2B4C, consisting of four sodium carboxylate groups and multiple freely rotating benzene rings, demonstrates outstanding solubility in anti-icing fluids and exhibits no fluorescent background signal even at low temperatures (<−20°C). Upon freezing, TPE-2B4C relocates from the water phase to higher viscosity ethylene glycol, causing restriction of benzene rings and a significantly increased green fluorescence signal. TPE-2B4C can successfully determine whether the anti-icing fluids are icing from −5 to −20°C with a high contrast ratio. Due to its simple setup, fast operation, and broad applicability, our new method is anticipated to be employed for rapid, real-time, and large-scale icing detection.